Since the beginning of 1990s, appearance and gradual promotion of lithium-ion battery have brought about, to some extent, rapid development of portable devices. In the recent ten years, due to quick improvement in safety and rate performance, power battery can be applied to various fields, such as large electric tools, hybrid motor vehicles and electric motor vehicles, etc., to work with high output torque motor, at least partially taking the place of power system that is dependent completely on combustion engines, which triggers a new round of upsurge in green energy resource.
Currently, due to concern about poor heat dissipation within a high capacity solid power battery, lithium-ion power batteries that have been commercialized in small scale usually have a unit capacity of 8-100 Ah, among which, typical lithium-ion power batteries include: SPIM24300260 100 Ah rectangular lithium-ion power battery from Citic Guoan Mengguli New Energy Science & Technology Co., Ltd., and IMP20/66/148-08PS 8Ah high-power battery from Phylion Battery (Suzhou) Co., Ltd. Based on these battery cells, a person in the art may increase the voltage and capacity of a battery pack by connecting battery cells in series and in parallel to meet demands in different fields. For example, Beijing Zhongweixintong Science & Technology Co., Ltd. has developed a UPS sample product ZWDY-48/300 which uses a 48V-300 Ah battery pack for telecom field, with the battery pack consisting of power unit cells with a unit capacity of 10 Ah.
EP1705743A1 relates to a battery module having a plurality of unit cells. In the battery module, the unit cells are spaced apart from each other by a predetermined distance and are connected in series or in parallel.
US2005/0174092A1 relates to a battery system for use in a vehicle, which includes a plurality of electrically connected lithium batteries. According to one embodiment, the battery system comprises a module that includes a plurality of (e.g. ten) lithium batteries electrically connected in series. According to another embodiment, the module may be coupled to a wire or a cable via a connector so as to connect the module to another module or to a vehicle electrical system.
Nevertheless, the power output characteristic of the existing solid power battery still cannot fulfill the requirements in some high-level fields, such that engineers could only obtain the desired high power output characteristic by decreasing cell capacity, providing clearance and adopting forced ventilation. A typical example is the electric motor vehicle “Tesla Roadster” produced by the US Tesla Motors, which entered mass production in March, 2008. In order to realize acceleration from rest to a speed of 100 km/h within 4 s, its battery pack uses the currently most mature 18650-type lithium-ion battery cells, and as many as 6831 such 18650-type lithium-ion battery cells are used for each motor vehicle. Obviously, this greatly increases complexity of the power management system, complexity of assembly and maintenance of the battery pack as well as reliability of whole power system.
With further reduction in product cost of power battery products in future years, when the application of power battery products is extended to fields of energy storage and peak regulation in power stations, power network filtering, emergency power for electric locomotive and so on, it is almost impossible to image how to combine cells with a capacity less than 100 Ah together to meet power requirement up to MW level in these fields.
As an improvement, U.S. Pat. No. 5,501,916A discloses a battery cell, wherein a through-hole is provided in the battery core, and a lid forming the battery shell is closely attached, directly or via aluminum plate(s) that are thermally connected to the lid, to at least a part of sidewall of the through-hole in the battery core, thereby heat dissipation within the cell can be improved.
However, it should be noted that, provision of a through-hole as mentioned in the above patent is not the key point for solving the problem of heat dissipation. The key for solving the heat dissipation problem is to limit the maximum thickness of the battery core. Although the maximum thickness of the battery core may be reduced by providing a through-hole, for the cases where the capacity of a battery cell increases up to more than 300 Ah or the maximum thickness of a solid battery core is equal to or greater than 100 mm, due to limitation to the maximum thickness of the battery core imposed by safety and rate performance requirement, simply increasing the diameter or the number of through-holes may solve the problem of heat dissipation within the battery, nevertheless bring about other problems. For example, an increase of through-hole diameter will increase the void (ineffective) volume in the through-hole, resulting in a reduction of energy density and power density of the battery cell and consequently of the entire battery pack, while an increase in number of through-holes will apparently increase manufacture difficulty and cost.